The present invention relates to improvements in cutter head assemblies for gear cutting machines. The invention permits use of faster and greatly simplified resharpening techniques for cutting blades by its provision for cutter head assemblies which are specifically designed and constructed to accommodate cutting blades which can be resharpened without removal of material from their cutting faces.
It is known in the art of gear cutting machines to provide various designs of individual cutting blades to be fitted in a cutter head assembly so that the cutting blades can function to generate tooth profiles in a workpiece. Typically, the cutting blades used with such cutter head assemblies have been relatively complex in their design and have been costly to resharpen and replace because of the difficulty in maintaining critical angular relationships between front, end, and side faces of each cutting blade. Cutter head assemblies for such blades have been, on the other hand, relatively simple.
Numerous attempts have been made to reduce the initial and resharpening costs of cutting blades for various types of milling cutters. For example, it is known to place individual cutting blades in radially inclined slots in a milling head assembly for the purpose of establishing a pre-set pressure angle for each blade without a requirement for a regrinding of the surface which establishes such an angle (see U.S. Pat. No. 3,673,655). Other types of milling tools have provided for an angular placement of cutting blades in a cutter head so as to establish rake and shear angles for a front face of the cutting blades (see U.S. Pat. No. 2,186,417).
The present invention is specifically concerned with improvements in cutter head assemblies designed for use in gear cutting machinery capable of generating tooth profiles for spiral, bevel and hypoid gears. In applications of this type, dimensional relationships of the cutting tools are extremely critical and must be maintained to close tolerances in order to obtain a desired tooth profile for each tooth and slot of the final gear product. One of the relationships which must be carefully maintained is the angle and position of the cutting face (or chip face) of each cutting blade relative to the cutter head assembly in which it is carried and to the workpiece which is being cut. Although cutting blades of the type shown in U.S. Pat. No. 2,186,417 require no resharpening of their front faces, it is believed that all prior efforts in designing and resharpening cutting tools for gear cutting applications have required a careful resharpening of the cutting face each time the cutting tool is resharpened for further usage in a cutter head assembly (see, for example, U.S. Pat. No. 3,487,592). This requirement of past designs not only adds to the cost of use of a particular tool, but also prevents the usage of certain hard coatings on a steel substrate because such coatings would be removed during the resharpening process.
In contrast to prior art methods and means, the present invention provides for a novel cutter head assembly which permits use of individual cutting blades which can be easily resharpened in such a manner that all of the critical relationships required for gear cutting applications are maintained while a front face surface of each cutting blade is preserved during each resharpening. Blades of this type not only eliminate the cost and difficulty of resharpening the critical front face parameter for each cutting blade tool but also permit the use of unusual material combinations or treatments, such as titanium carbide or chromium coatings with high speed steel substrates, for cutting tools having longer life and greater strength.
Thus, a cutter head assembly is specifically designed in accordance with the present invention to receive a type of individual cutting blade which can be sharpened without removing material from a cutting face (or chip face) thereof. The cutter head assembly is characterized by an arrangement of blade-receiving slots set at angles to correspond to front face angles for each cutting blade relative to its contact with a workpiece so that the cutting blades can be removed, resharpened and replaced into such slots without removing, any stock from their cutting faces.
In a specific embodiment of the invention, a cutter head assembly is provided with a plurality of clamping slots formed into its periphery for receiving clamping members which secure cutting blades in the assembly. Two or more blade-receiving slots are formed in communication with each clamping slot so that blades can be arranged to cut different portions of a slot.
These and other features and advantages of the present invention will become apparent in the more detailed discussion which follows. In that discussion reference will be made to the accompanying drawings as briefly described below.